OBJECTIVE: To determine whether developmentally related cytoplasmic changes occur during early embryo development in primate embryos, using multiphoton microscopy to image mitochondria in living rhesus oocytes and embryos. RESULTS We have identified specific types of mitochondrial distribution in rhesus oocytes and embryos that are compatible with development to the blastocyst stage. The use of multiphoton microscopy allows us to directly correlate later events (development) with earlier events (cytoplasmic organization) in the same embryo. KEY WORDS mitotracker, rhesus monkey, oocyte maturation, embryo, blastocyst